// Copyright 2018 Yuya Nishihara <yuya@tcha.org>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//! Utility for parsing and building command-server messages.

use std::error;

use std::ffi::{OsStr, OsString};

use std::io;

use std::os::unix::ffi::OsStrExt;

pub use tokio_hglib::message::*; // re-exports

/// Shell command type requested by the server.

#[derive(Clone, Copy, Debug, Eq, PartialEq)]

pub enum CommandType {

    /// Pager should be spawned.

    Pager,

    /// Shell command should be executed to send back the result code.

    System,

}

/// Shell command requested by the server.

#[derive(Clone, Debug, Eq, PartialEq)]

pub struct CommandSpec {

    pub command: OsString,

    pub current_dir: OsString,

    pub envs: Vec<(OsString, OsString)>,

}

/// Parses "S" channel request into command type and spec.

pub fn parse_command_spec(data: Bytes) -> io::Result<(CommandType, CommandSpec)> {

    let mut split = data.split(|&c| c == b'\0');

    let ctype = parse_command_type(split.next().ok_or(new_parse_error("missing type"))?)?;

    let command = split.next().ok_or(new_parse_error("missing command"))?;

    let current_dir = split.next().ok_or(new_parse_error("missing current dir"))?;

    let mut envs = Vec::new();

    for l in split {

        let mut s = l.splitn(2, |&c| c == b'=');

        let k = s.next().unwrap();

        let v = s.next().ok_or(new_parse_error("malformed env"))?;

        envs.push((

            OsStr::from_bytes(k).to_owned(),

            OsStr::from_bytes(v).to_owned(),

        ));

    }

    let spec = CommandSpec {

        command: OsStr::from_bytes(command).to_owned(),

        current_dir: OsStr::from_bytes(current_dir).to_owned(),

        envs: envs,

    };

    Ok((ctype, spec))

}

fn parse_command_type(value: &[u8]) -> io::Result<CommandType> {

    match value {

        b"pager" => Ok(CommandType::Pager),

        b"system" => Ok(CommandType::System),

        _ => Err(new_parse_error(format!(

            "unknown command type: {}",

            decode_latin1(value)

        ))),

    }

}

fn decode_latin1<S>(s: S) -> String

where

    S: AsRef<[u8]>,

{

    s.as_ref().iter().map(|&c| c as char).collect()

}

fn new_parse_error<E>(error: E) -> io::Error

where

    E: Into<Box<error::Error + Send + Sync>>,

{

    io::Error::new(io::ErrorKind::InvalidData, error)

}

#[cfg(test)]

mod tests {

    use super::*;

    use std::os::unix::ffi::OsStringExt;

    #[test]

    fn parse_command_spec_good() {

        let src = [

            b"pager".as_ref(),

            b"less -FRX".as_ref(),

            b"/tmp".as_ref(),

            b"LANG=C".as_ref(),

            b"HGPLAIN=".as_ref(),

        ]

        .join(&0);

        let spec = CommandSpec {

            command: os_string_from(b"less -FRX"),

            current_dir: os_string_from(b"/tmp"),

            envs: vec![

                (os_string_from(b"LANG"), os_string_from(b"C")),

                (os_string_from(b"HGPLAIN"), os_string_from(b"")),

            ],

        };

        assert_eq!(

            parse_command_spec(Bytes::from(src)).unwrap(),

            (CommandType::Pager, spec)

        );

    }

    #[test]

    fn parse_command_spec_too_short() {

        assert!(parse_command_spec(Bytes::from_static(b"")).is_err());

        assert!(parse_command_spec(Bytes::from_static(b"pager")).is_err());

        assert!(parse_command_spec(Bytes::from_static(b"pager\0less")).is_err());

    }

    #[test]

    fn parse_command_spec_malformed_env() {

        assert!(parse_command_spec(Bytes::from_static(b"pager\0less\0/tmp\0HOME")).is_err());

    }

    #[test]

    fn parse_command_spec_unknown_type() {

        assert!(parse_command_spec(Bytes::from_static(b"paper\0less")).is_err());

    }

    fn os_string_from(s: &[u8]) -> OsString {

        OsString::from_vec(s.to_vec())

    }

}